NAME

mac_lso_get — get LSO information on message blocks

SYNOPSIS

#include <sys/mac_provider.h>

void
mac_lso_get(mblk_t *mp, uint32_t *mss, uint32_t *flags);

INTERFACE LEVEL

illumos DDI specific

PARAMETERS

mp: A pointer to a mblk(9S) structure that contains an outgoing frame.
mss: A pointer to a value that will be filled in with the maximum segment size (MSS).
flags: A pointer to a value that will be filled in with various flags that indicate the behavior to perform.

DESCRIPTION

The mac_lso_get() function is used by device drivers that have indicated that they support the MAC_CAPAB_LSO capability to determine whether large send offload (also known as large segmentation offload or LSO) is required for this frame or not. If so, the driver should take the appropriate actions to program the hardware to perform LSO.

The mac_lso_get() function should only be called on the first mblk_t that begins a given individual frame in a chain. In other words, it only works on entries where it is the first of many possible entries linked together by the b_cont member. The first mblk_t received from any mac(9E) API or pointed to by a b_next pointer should be used.

A device driver should first look at the flags argument to determine what to do. flags may be a bitwise inclusive OR of the following:

HW_LSO: This flag indicates that hardware needs to perform segmentation offload. The maximum segment size that the driver should use is available through the mss argument.

CONTEXT

The mac_lso_get() function may be called from user, kernel, or interrupt context.